1. Field of the Invention
The present invention relates to a surface mounting quartz-crystal oscillator, which will be hereinbelow, referred to as a surface mounting oscillator, and more particularly, relates to a surface mounting oscillator having a superior productivity.
2. Description of the Prior Art
A quartz-crystal oscillator is formed as an oscillator unit in which a quartz-crystal element and an IC (an integrated circuit) chip which constitutes an oscillator circuit containing therein the quartz-crystal element are accommodated together in a common container. These type of quartz-crystal oscillators are widely used as frequency and time reference sources for many electronic appliances including telecommunication equipment. In the quartz-crystal oscillators, the surface mounting oscillator is usually adopted by small portable electronic appliances represented by, for example, cellular phones, and a demand for the surface mounting oscillator is expected to increase from now on. Thus, the surface mounting oscillator is requested particularly to have superior productivity, and additionally to reduce its height upon being mounted in order to enable the surface mounting oscillator to be mounted at a high mounting density.
FIGS. 1 and 2 are exploded perspective and cross-sectional views illustrating a conventional surface mounting oscillator, respectively.
The surface mounting oscillator of the prior art is provided with container body 1 made of laminated ceramics and accommodating therein quartz blank 2 and IC chip 3, and cover 6 attached to container body 1 to thereby hermetically encase quartz blank 2 and IC chip 3 within container body 1. Container body 1 is formed with recess 1a in which quartz blank 2 and IC chip 3 are received, and a couple of opposing sidewalls of the recess 1a provide a couple of steps 1b formed therein. IC chip 3 received in recess 1a has opposed ends held to bottom face 1c of recess 1a by the method of a face-down-bonding utilizing ultrasonic thermocompression bonding. Further, quartz blank 2 is held to one of steps 1b of recess 1a by conductive adhesive 7. Both ends of IC chip 3 are formed with a plurality of terminal electrodes (not shown) and bumps for conducting the ultrasonic thermocompression bonding. One of the longitudinal ends of quartz blank 2 is provided with laterally opposite sides in which extending electrodes 5 extending from excitation electrodes 4 are formed. Excitation electrodes 4 are arranged in both major surfaces of quartz blank 2. Extending electrodes 5 are fixedly bonded to the above-mentioned step 1b by electro-conductive adhesive 7 so that quartz blank 2 are held on step 1b. Cover 6 is attached and fixed to the container body 1 by, for example, seam-welding. In this case, metallic ring 8 for the purpose of welding is provided on the upper face of container body 1. The assignee of the present Patent Application has already disclosed in U.S. Ser. No. 09/651,023 and U.S. Ser. No. 09/651,026 an arrangement for surely connecting IC chip 3 of the surface mounting oscillator to the bottom face of the recess of the container body, and therefore the disclosure thereof will be hereby incorporated herein by reference.
Nevertheless, in the above-described arrangement of the surface mounting oscillator, IC chip 3 is firstly mounted to bottom face 1c of the recess of container body 1 and thereafter, quartz blank 2 is fixedly bonded to step 1b of the recess. Therefore, when it is found that after the bonding of quartz blank 2 acting as a quartz crystal element, the oscillating property thereof is inferior and not acceptable, high-priced IC chip 3 must be scrapped together with the quartz crystal element, resulting in such a problem that a reduction in productivity occurs which brings about an increase in the manufacturing cost of the surface mounting oscillator. At this stage, since the property of the quartz crystal element such as frequency-temperature characteristic is greatly affected by the holding or bonding condition of quartz blank 2, the property of the quartz crystal element cannot be evaluated until after quartz blank 2 is held by step 2. Further, when quartz blank 2 is bonded, conductive adhesive 7 is applied also to the upper face of quartz blank 2 for the purpose of increasing the bonding strength. This fact prevents the entire height of the surface mounting oscillator from being kept as small as possible.
An object of the present invention is therefore to provide a surface mounting oscillator having superior productivity.
Another object of the present invention is to provide a surface mounting oscillator having a height smaller than that of the prior art while enabling it to increase the mounting density thereof.
The above objects of the present invention will be achieved by a surface mounting quartz-crystal oscillator including a container body formed therein with a recess having a couple of opposite sidewalls in which steps are formed, a quartz blank, an IC (integrated circuit) chip constituting an oscillator circuit containing therein a quartz crystal element made of the quartz blank, and a cover for sealing the quartz crystal element and the IC chip within the container body, wherein one end of the quartz blank is bonded to a bottom face of the recess, opposite ends of the IC chip are fixedly held to the steps, and at least a part of the quartz blank is disposed in a space defined between the IC chip and the bottom face of the recess.
According to the described construction and arrangement, during the manufacturing of the surface mounting quartz-crystal oscillator, the IC chip can be mounted in the container body after the quartz blank is accommodated in the recess. Therefore, after the securing of the quartz blank but before the mounting of the IC chip, the property of the quartz crystal element can be examined to determine whether the quartz crystal element is good or bad. As a result, when the quartz crystal element is determined to be bad by the examination, the quartz crystal element may be cast aside so as to omit it from the succeeding manufacturing process. Accordingly, the high-priced IC chip can be prevented from being wasted while increasing the productivity of the surface mounting quartz-crystal oscillator.